Playing Blue Ray DVD

In synaptich all packages are present for playing Blue Ray. Most Blue Ray DVDs play well but some not (2019) the error is: No valid processing key found in AACS configuration file.
While this file is present. Any solution or what is going wrong?

Linux lacks a lot of support for proprietary stuff of all sorts. In this case, it is lacking decoding keys.

Thank you all for the replies/support.
I accept that there is no easy solution for this error.I’ll keep it this way…